Laboratory flash still for heavy oils



Iiun 16, 1953 J. .1. PIROS LABORATORY FLASH STILL FOR OILS 2 Sheets-Sheet 1 Filed April 5, 1949 Fee um T/N a MANDM E TE R Joy/v.7 P/Ros BY I INVENTOR ATTORN EY5 J. J. PIROS LABORATORY FLASH STILL FOR HEAVY OILS June 16 1953' F'iled April 5, 1949 2 Sheets-Sheet 2 Q35 E5333 3 mK INVENTOR Jo HN J P0205 M A ORNEYS Patented June 16, 1953 LABORATORY FLASH STILL FOR HEAVY OILS John J. Piros, Homewood, Ill., assignor, by mesne assignments, to Sinclair Research Laboratories Inc., Harvey, 111., a corporation of Delaware Application April 5, 1949, Serial No. 85,483

3 Claims.

This invention relates to a method and apparatus for the analytical flashing of a heavy oil. In one aspect, my invention provides for a method of evaluating the asphalt content of a heavy crude oil while, in another, it provides an equilibrium flash still automatically maintained under adiabatic flash conditions by a mercury vapor heating medium and which is useful for such an evaluation.

Generally speaking, it is diflicult to obtain a clean out in the separation of asphalt from a heavy crude by distillation and thus determination of asphalt content requires a large amount of the oil. This is due, in part, to the fact that adiabatic flash conditions, which are highly desirable, have only been roughly approximated in conventional practice. And, in addition, a distillation of this nature is a tedious manual operation wasteful of time and eflort.

I have now discovered an improved method whereby the asphalt content of a small amount of a heavy petroleum fraction can be accurately appraised by flashing in a reduced pressure flash zone automatically maintained under adiabatic conditions by use of a mercury vapor heating medium. Adiabatic flash conditions are attained when the mercury vapor heating medium is automatically controlled by means responsive to,

and corrective oi, temperature changes in the zone. In addition, l'provide an equilibrium flash still adaptable to this asphalt determination.

An embodiment of my invention comprises introducing a small measured quantity of a heavy petroleum fraction, advantageously preheated, into a reduced pressure flash zone maintained under adiabatic conditions by use of a mercury vapor heating medium automatically controlled by means responsive to, and corrective of, temperature changes in the zone, taking ofl from this zone a light ends product and, separately, a heavy ends product, this withdrawal being eifected by the maintenance of equalized subatmospheric pressures at both take-offs.

The mercury vapor-heated flash zone is automatically maintained under adiabatic conditions by means responsiv to the temperature or pressure of the mercury vapor medium which circulates in enclosed chambers throughout the flash zone. For instance, the pressure over the mercury is reduced and the mercury initially heated to the desired flash temperature. To overcome temperature variations due to the flashing, a pressure-actuated automatic control device, such as a make-break regulating manometer, may he used wherein the manometer, by a change in the height of the mercury column (correspond- .maintain such contact.

taining chambers so that liquid mercury in the lower portion thereof flows into the manometer tube. The other end of the manometer tubeis open to the atmosphere. The vaporpressure of the confined mercury is balanced against atmos-.

pheric pressure by the column of liquid mercury in the open end of the manometer tube. A pair of electrical contacts are placed in the mercury confining chambers, one at all times being mersed in the liquid mercury, and the other being pressures exceeding that measured by the height of a column of mercury in the tube necessary to The electrodes, when both are in contact with mercury, complete an electrical circuit which actuates a relay orother -mechanism used to control the heating element immersed in the mercury. .Such control is arranged so that closing the circuit, by contact of the mercury column with both electrodes, turns off the heating element, and opening the circuit, by dropping of the column of mercury to below the height necessary to contact the upper electrode, turns on the heating circuit.

The automatic adiabatic conditions main-'- tained by the mercury vapor heating mediu provide a highly satisfactory flash zone for several reasons. In particular, a uniform temperature is insured throughout the entire flash zone,

thereby avoiding localized hot spots which may cause objectionable thermal cracking. satisfactory equilibrium conditions are attained within'a short period of time and are easily so maintained without requiring constant and considerable attention.

A preferred embodiment of my invention is anequilibrium flash still comprising essentially a flash zone with separate take-offs for the light and heavy ends. Advantageously, a preheat zone.

is employed prior to flashing of the oil and it may be integral with the flash zone, although.

Further,

vapor throughout its interior, although not in direct contact with the petroleum constituents.

The accompanying drawings will serve to better illustrate my invention. Figures 1 and 2 illustrate an embodiment of the equilibrium flash still while Figure 3 illustrates a somewhat diagrammatic. flow diagram of a process wherein relatively small amounts of a petroleum fraction may be measured for asphalt content.

The still is shown in detail in Figure 1; Figure 2 illustrates an enlarged cross-sectional view of the column insulation and heating means. The apparatus so illustrated is composed mainly of a low heat capacity material, most advantageously glass.

The equilibrium flash still comprises essentially a flash zone [2 preferably integral with an upper preheat zone II. The preheat zone ll containsan inner coiled glass tube 13 through which the feed material passes from outside connection 39. The tube I3 is coiled within cylindrical glass tube 14, which extends the length of the preheat zone ll. Heating means I5, composed of nichrome wire within a ceramic form, surrounds the outside of the cylindrical glass tube l4 for its entire length. The pre-- heat zone advantageously contains a temperature recording means, thermowell I6, extending through the flash zone so as to terminate at about the bottoms product take-off in the flash zone and is connected externally at 4B. Tube l3, as it extends through preheat zone II, is coiled about thermowell l6 and terminates in an envelope 8|, positioned coaxially about thermowell I6 and opening into the interior central section I9 of the flash zone at 82. Connection 4] is provided to measure the pressure within the still as well as to remove ob- J'ectionable fluids. The upper part of the enlarged flash zone contains an interior take-off I! for the flashed light ends which leads to an external connection by means of line 18. The flashed heavy bottoms pass through the interior central section IQ of the flash zone and are conducted to an exterior take-off connection by means of line 20. Surrounding the petroleum fraction being flashed, but not in direct contact with it, is mercury vapor circulating in chambers 23 and 24, supplied by mercury well 2!. The well 2| is filled and the mercury chambers evacuated by means of line 25 and valve 28. The mercury is maintained at a constant temperature most advantageously by means of a makebreak regulating manometer 21. This arrangement includes a manometer 21 in open connection with mercury well 2| at one end and open to the atmosphere at the other. The upper portion of manometer 21 is connected to relay '28 by movable contact 29 inserted into the column. Depending upon the level of the mercury in the manometer tube, heating element 50, immersed and extending into the depressed portion of the still, is actuated by movable contact 29 through the relay 28 by closing of a circuit between contact 43 and contact 29 through the mercury in the manometer tube. That is, closing the circuit opens the heating circuit, while opening the relay circuit closes the heating circuit.

The flash chamber wall 42 is preferably insulated, as illustrated in Figure 2. The insulation consists of an initial covering with glass tape an, and is then covered with nichrome wire 3|, glass insulation 32, and finally, with glass ribbon 33.- This provides an insulation and heating means that will minimize heat loss and thereby decrease the load on the mercury heating medium. In addition, the remainder of the flash still may be similarly insulated and heated. Skin thermocouples 36, 31, 38, 44, and 45 are located at a variety of places so as to provide useful temperature data.

The equilibrium flash still is operated as follows: Valve 25 is opened and liquid mercury is charged into well 2| through line 25 to about level 22. The mercury vapor circulating system, including chambers 23 and 24, is evacuated to a subatmospheric pressure corresponding to the vapor pressure of mercury at the existing room temperature. The mercury vapor heating element to, as well as the column heating means, are turned on and the mercury vapor is allowed to reach the desired operating temperature. The movable contact 29 is then lowered into the mercury vapor regulating manometer 21 so as to make contact with the mercury at the desired pressure necessary to maintain the operating temperature. The temperature of the preheat zone H is appropriately adjusted, by regulating the nichrome heating means [5, so that the preheat temperature is higher than the flash temperature, in order to provide the energy required for partial vaporization of the charge. Following this, the flash zone I2 is evacuated to the desired operating pressure and the feed is introduced through connection 39.

Figure 3 illustrates, somewhat diagrammatically, a process wherein a small amount of a petroleum fraction may be evaluated for asphalt content.

A small quantity of petroleum feed, say, a reduced crude, is charged to feed burette 52, heated therein, for instance, to 250 F., measured, passed by means of line 79 and pump 69 to a preheat zone and then to the flash zone, these two zones being advantageously made up as one unit. Pump 69 may operate at a suction temperature of about 300 F.; line 'lil is insulated with a nichrome ribbon and glass tape 'H so as to prevent a heat loss. The charge is advantageously preheated in preheat zone I! and then flashed in flash zone 1'2. The preheat and flash zones II and I2, may be made up as the flash still 5! described in detail in Figures 1 and 2. The charge is preheated in the preheat zone to a temperature higher than the flash temperature as measured in the flash zone I2. This excess temperature is necessary to provide the energy required for partial vaporization of the charge. The charge is then flashed in flash zone 12 at a temperature of about 720 F. and at a reduced pressure. The petroleum fraction is thus separated into a light ends product, removed by line 12, and a heavy ends product, taken oiT by line 60. This withdrawal is effected by means of equalized subatmospheric pressures maintained at both take-offs by vacuum means, preferably pump 6|. The light ends pass to condensing zone 53, where they are condensed, and are then passed to receiving zone 59. The uncondensed light ends are advantageously knocked back by kickback condensing zone 5% and by a Dry Ice-acetone cooled condensing zone 6'5. The heavy ends flow to receiving zone 13.

Stopcocks 14 and 15 may be provided for the receiving zones, so that these zones or chambers may be removed, replaced, and new chambers, evacuated by vacuum means, advantageously pump on vacuum pump 62, cut in with a minimum of interference. Three way stopcocks l6 and 11, in lines 18 and 80, are employed so that the receiving zones may be vented to atmospheric pressure or pumped out by pump 62 to the operating pressure. The pressure on the system may be regulated, say, by a cartesian-diver manostat 63 in line 19; this pressure may be measured by Dubrovin gauge 64 in the line from connection 4|. Oil trap 68, liquid trap 66, and carbon dioxide trap 67 serve to remove objectionable fluids.

In a process as described, a, highly satisfactory feed rate is within the range of about 200 to 400 cc. per hour; however, the actual feed used is dependent in great part upon the feed and flash temperatures employed.

I claim:

1. A continuous equilibrium flash still for the flashing of a petroleum fraction which comprises a preheat zone and a flash zone, an'en closed mercury vapor circulating system connected to said flash zone having a mercury well and a mercury vapor chamber extending upwardly from said mercury well into said flash zone, said mercury vapor chamber being annular in form and completely dividing said flash zone into an interior central section and an exterior annular section, means for maintaining the mercury at a predetermined temperature including,

a make-break manometer connected to and in open communication with said mercury well at one end and open to the atmosphere at the other end, and a heating'el'ement immersed in said mercury and controlled by said make-break manometer for supplying the necessary heat to said mercury, a charge pipe extending downwardly from said preheat zone into said interior central section of said flash zone for delivering the petroleum fraction thereto for flashing, means for removing the light ends product from the flash zone, and means for removing the heavy ends product from the flash zone.

2. A continuous equilibrium flash still for the flashing of a petroleum fraction which comprises a preheat zone and a flash zone, an enclosed mercury vapor circulating system connected to said flash zone having a mercury well and a mercury vapor chamber extending upwardly from said mercury well into said flash zone, said mercury vapor chamber being annular in form and completely dividing said flash zone into an interior central section and an exterior annular section, means for maintaining the mercury at a predetermined temperature including a makepreheat zone into said interior central section of said flash zone for delivering the petroleum fraction thereto for flashing, a first take-ofi connection connected to said flash zone and communicating with said exterior annular section for removing the light ends product from the flash zone, a second take-off connection connected to said flash zone and communicating with the bottom of said interior central section for removing the heavy ends product from the flash zone, and means for maintaining said first and second take-oil. connections at equalized subatmospheric pressures.

3. Acontinuous equilibrium flash still for the flashing of a petroleum.fraction which comprises a flash zone, an enclosed mercury vapor circulating system connected to said flash zone having a mercury well and a mercury vapor chamber extending upwardly from said mercury well into said flash zone, said mercury vapor chamber being annular in form and dividing said flash zone into an interior central section and anexterior annular section, means for maintaining the mercury at a predetermined temperature including a make-break manometer connected to and in open communication with said mercury well at one end and open to the atmosphere at the other end, and'a heating element immersed in said mercury and controlled by said make-break manometer for supplying the necessary heat to said mercury, a charge pipe connected to said flash zone and extending downwardly into said interior central section for delivering the petroleum fraction thereto for flashing, means surrounding the upper portion of said charge pipe for preheating the petroleum fraction to provide the energy needed for the flashing of the charge in said interior central section, a first take-oil connection connected to said flash zone and communicating with said exterior annular section for removing the light ends product from the flash zone, a second take-off connection connected to said flash zone and communicating with the bottom of said interior central section for removing the heavy ends product from the flash zone, and means for maintaining said first and second take-ofi connections at equalized subatmospheric pressures. V

JOHN J. PIROS.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Winters et al., Ind. and Eng. Chem. Anal. ed., vol. 9 (1937), pp. 189, 190.

Nelson et al., Ind. and Eng. Chem. Anal.

f d. vol. 9 (1937), p. 402. 1 

1. A CONTINUOUS EQUILIBRIUM FLASH STILL FOR THE FLASHING OF A PETROLEUM FRACTION WHICH COMPRISES A PREHEAT ZONE AND A FLASH ZONE, AND ENCLOSED MERCURY VAPOR CIRCULATING SYSTEM CONNECTED TO SAID FLASH ZONE HAVING MERCURY WELL AND A MERCURY VAPOR CHAMBER EXTENDING UPWARDLY FROM SAID MERCURY WELL INTO SAID FLASH ZONE, SAID MERCURY VAPOR CHAMBER BEING ANNULAR IN FORM AND COMPLETELY DIVIDING SAID FLASH ZONE INTO AN INTERIOR CENTRAL SECTION AND AN EXTERIOR ANNULAR SECTION, MEANS FOR MAINTAINING THE MERCURY AT A PREDETERMINED TEMPERATURE INCLUDING A MAKE-BREAK MANOMETER CONNECTED TO AND IN OPEN COMMUNICATION WITH SAID MERCURY WELL AT ONE END AND OPEN TO THE ATMOSPHERE AT THE OTHER END, AND HEATING ELEMENT IMMERSED IN SAID MERCURY AND CONTROLLED BY SAID MAKE-BREAK MANOMETER FOR SUPPLYING THE NECESSARY HEAT TO SAID MERCURY, A CHARGE PIPE EXTENDING DOWNWARDLY FROM SAID PREHEAT ZONE INTO SAID INTERIOR CENTRAL SECTION OF SAID FLASH ZONE FOR DELIVERING THE PETROLEUM FRACTION THERETO FOR FLASHING, MEANS FOR REMOVING THE LIGHT ENDS PRODUCT FROM THE FLASH ZONE, AND MEANS FOR REMOVING THE HEAVY ENDS PRODUCT FROM THE FLASH ZONE. 